Plasticized polyvinyl butyral sheet (PVB) is used in the manufacture of laminate structures such as, for example: windshields for vehicles including automobiles, motorcycles, boats and airplanes; homes and buildings; shelving in cabinets and display cases; and other articles where structural strength is desirable in a glass sheet. In many applications, it is desirable that the laminate be transparent and colorless. In other applications it can be desirable for the laminate to be translucent. Translucent laminates have been known in the art of laminated safety glass for many years.
Typically, translucent laminates have light transmission levels of 70 percent or less. However, translucent or semi-transparent laminates having higher light transmission levels, for example from 80 to 90 percent transmission—and also with high light diffusion properties—are typically prepared using sandblasted or etched glasses.
Sandblasting is a process that can be used for making glass less transparent by bombarding the surface of the glass with high-velocity sand particles, glass beads or similar aggregate, propelled under pressure from a sandblasting apparatus. Etching is a process by which the surface is chemically etched by application of a chemical, such as an acid which reacts on the surface of the glass to reduce the transparency in the areas where the chemical contacts the glass surface. Either of these processes can create a roughened surface on the glass, thereby causing a scattering, or diffusion, of incident light at the surface of the glass.
While the processes of sandblasting and etching can create glass with from low to high opacity, and with light diffusion and light transmission properties offering aesthetic appeal in architectural applications, the processes themselves can be dangerous because of the handling of the etching acids and/or silicosis from the glass dust created. Further, any operation that creates imperfections in the glass surface creates stresses that can lead to failures of the glass when handled or impacted, thereby reducing its safety properties. An additional problem encountered with glass having a roughened surface is that the surface can be difficult to clean where dirt becomes trapped in creases on the glass.
Typically, commercially available white intertayers have a very low level of light transmission. In fact, white interlayer products that are commercially available allow light to pass through but do not allow a person to recognize or discern the shape of an object through the interlayer, or through any laminate prepared therefrom.
It would be desirable to have a translucent, or semi-transparent, glass laminate that affords some measure of object recognition through the laminate, wherein the laminate has the aesthetic characteristics of sandblasted or etched glass, and at the same time has the strength of a standard transparent safety glass laminate.
It would also be desirable to obtain such an aesthetically pleasing laminate by a process that reduces or eliminates the safety risks associated with manufacturing sandblasted or etched glass.